Originally Posted by
khatfull
Well, it wasn't the spring. Here's a video of the RD to demonstrate the spring tension:
I replaced the chain with an SRAM PC830 just for grins after working on the length a little more...much better now, both in terms of length and shifting.
I really wanted to use that KMC chain...the RD just must not have liked it...no wear at all according to the gauge.
Those derailleurs were made to work with a wide, stiff, chain, the old Reginas. They will shift better with a freewheel with a modern tooth, like a Sachs or Shimano, but that 6-speed chain should be what it was made for. Length is the issue, not chain type. A narrower chain should require more overshift, anyway.